Fuel dispensers in retail service station environments include flow meters that measure the volumetric flow rate of fuel as it is dispensed. Such flow meters are typically required to comply with weights and measures regulatory requirements that mandate a high level of accuracy. This ensures that the customer is neither overcharged nor undercharged for the fuel purchase. Typically, either positive displacement meters or inferential meters have been used for this purpose.
In modern service station fuel dispensers, a control system processes signals generated by a displacement sensor to monitor the amount of fuel delivered to a customer's vehicle. Various types of displacement sensors have been used to sense the flow rate of various fluids, including magnetic sensors and optical sensors. One such displacement sensor is referred to as a pulser. Pulsers are sensors operatively connected to the flow meter to measure rotation of a flow meter shaft. As fuel is dispensed, causing the shaft to rotate, the pulser generates a pulse train. Each pulse represents a known volume of fuel (e.g., 0.001 gallons) passing through the meter.
Attempts have been made to interfere with the displacement sensor on a fuel flow meter in order to modify the calculated volume of fuel dispensed. For example, a dishonest consumer may disconnect the displacement sensor (or one of its components) from the fuel flow meter prior to a fueling transaction. Also, a dishonest consumer may disable either or both of the fuel dispenser or displacement sensor electronics and force fuel through the fuel flow meter.
Often, mechanical means are used to prevent detachment of the displacement sensor from the fuel flow meter. For example, commonly-owned U.S. Pub. App. No. 2009/0314804 to Kinzie et al., incorporated by reference herein in its entirety for all purposes, discloses a lockable enclosure for protecting a pulser of a fuel dispenser. Alternatively, locks and pins on the meter and pulser have been used for this purpose.